Photocurable resin composition

ABSTRACT

Disclosed is a photocurable composition comprising (a) a radical-polymerizable monomer, (b) an α-ketocarbonyl compound and (c) a derivative of mercaptobenzimidazole, mercaptobenzothiazole or mercaptobenzoxazole or an aromatic amine nucleus-substituted with an electron-attractive group. This composition has a high photocuring speed at a temperature close to normal temperature and gives a cured product excellent in various physical properties. This composition is valuable as a dental adhesive or resin.

.Iadd.This application is a continuation of now abandoned applicationSer. No. 07/770,528, filed Oct. 3, 1991 which is a reissue of U.S. Pat.No. 4,548,689, issued Oct. 27, 1985 (Ser. No. 06/654,243, filed Sep. 25,1984). .Iaddend.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a photocurable resin composition whichis excellent in the photo-curability at low temperatures close to normaltemperature and provides a cured product excellent in the adhesioncharacteristics such as the water-resistant adhesion strength and alsoin the hardness, strength and color tone. More particularly, the presentinvention relates to a photocurable resin composition which showsexcellent properties as a curable composition for teeth, such as a toothadhesive, a tooth composite resin or a tooth rigid resin.

(2) Description of the Prior Art

Various curable compositions comprising a radical-polymerizable monomersuch as a (meth)acrylic acid ester type vinyl monomer and apolymerization initiator have been proposed as curable compositions forteeth, such as tooth adhesives, composite resins and rigid resins.

A tooth adhesive is required to have a high curing speed at lowtemperatures close to normal temperature and to provide a cured productexcellent in the adhesion strength to teeth and the water-resistantadhesion strength. A tooth composite resin or tooth rigid resin isrequired to have a curability at low temperatures close to normaltemperature and to provide a cured product which is excellent not onlyin the above-mentioned adhesion characteristics but also in themechanical properties such as strength, compression strength, hardnessand abrasion resistance and the color tone. With recent rapid progressof the tooth-repairing curative technique, the above-mentionedproperties required for curable compositions for teeth become severe.

In connection with conventional curable compositions for teethcomprising a radical-polymerizable monomer such as a (meth)acrylic acidester type vinyl monomer and a polymerization initiator, there have beenproposed several methods in which a photopolymerization initiator isused as the polymerization initiator and photocuring is effected,whereby the above-mentioned properties are improved. For example,Japanese Patent Publications No. 10986/79 and No. 33687/78 propose aprocess in which polymerization is carried out in the presence of aphotopolymerization initiator comprising a carbonyl compound such asα-diketone and an amine. Even if this known combination of a carbonylcompound and an amine is used for photocuring a radical-polymerizablemonomer of the (meth)acrylic acid ester type having an aromaticpolycarboxylic acid or its anhydride structure and the cured product isapplied to the above-mentioned uses of the photocurable resincomposition for teeth, no satisfactory results can be obtained becausethe cured product is inferior in the color tone and water-resistantadhesion strength.

Recently, Japanese Patent Application Laid-Open Specification No.5407/82 and DE-OS 3,029,276 teach that when a 2-cyanoethylamine,especially N-methyl-N-cyanoethylamine, is used as the amine promoter forthe photopolymerizable composition, the curing-promoting action isenhanced and there can be attained effects of preventing coloration ofthe cured resin and eliminating the amine smell.

We previously found that when a composition comprising aradical-polymerizable monomer including4-methacryloyloxyethoxycarbonylphthalic acid or its anhydride and avinyl compound and a free radical generator is used as a tooth adhesive,a cured product excellent in the adhesion characteristics such as theadhesion strength and water-resistant adhesion strength is obtained, andwe proposed this photocurable composition in Japanese Patent ApplicationLaid-Open Specification No. 12338/79 and Japanese Patent Publication No.17513/83.

This photocurable composition for teeth is excellent in the adhesioncharacteristics, mechanical properties and color tone but is stillinsufficient in the curing speed.

SUMMARY OF THE INVENTION

In view of the above-mentioned conventional curable compositions forteeth and the properties required for these compositions, we maderesearch with a view to ddveloping a photocurable composition excellentin the curing characteristics and capable of providing a cured productexcellent in the adhesion characteristics, mechanical properties andcolor tone. As the result, it was found that this object can be attainedby photocuring a composition comprising a radical-polymerizable monomer,an α-ketocarbonyl compound and a specific aromatic amine by irradiationwith light. We have now completed the present invention based on thisfinding.

The photocurable composition of the present invention has a highphotocuring speed at low temperatures close to normal temperature and isexcellent in the adhesion characteristics such as the adhesion strengthand water-resistant adhesion strength and this composition provides acured product excellent in the color tone and the mechanical propertiessuch as strength, compression strength, hardness and abrasionresistance. Accordingly, this photocurable composition has propertiesrequired for a curable composition for teeth, such as a tooth adhesive,a composite resin or a rigid resin and is suitable for tooth treatments.Furthermore, the photocurable composition of the present invention canbe used as an adhesive at the precision processing step, a metaladhesive or a composite resin in various fields. Moreover, if thepresent invention is applied to photopolymerization of theabove-mentioned radical-polymerizable monomer of the (meth)acrylic acidester type having an aromatic polycarboxylic acid or its anhydridestructure instead of a known ordinary radical-polymerizable monomer, theabove-mentioned excellent effects are further enhanced.

In accordance with the fundamental aspect of the present invention,there is provided a photocurable composition comprising (a) aradical-polymerizable monomer, (b) an α-ketocarbonyl compound and (c) anamine, wherein the amine (c) is at least one member selected from thegroup consisting of compounds represented by the following generalformula: ##STR1## wherein X stands for >NR², an oxygen atom or a sulfuratom, Y stands for a hydrogen atom, --SR³ or a monovalent, divalent ortrivalent metal, R¹ stands for an alkyl group, an aryl group, an aralkylgroup or a halogen atom, n is an integer of from 0 to 4 with the provisothat when n is 2 or larger, a plurality of groups R¹ may be the same ordifferent, R² stands for a hydrogen atom, an alkyl group, an aryl groupor an aralkyl group, and R³ stands for an alkyl group or an aryl group,or a group represented by the following general formula: ##STR2##wherein X, R¹ and n are as defined above, and substituted aminesrepresented by the following general formula: ##STR3## wherein R⁴ standsfor a hydrogen atom or an alkyl group, R⁵ stands for a hydrogen atom, analkyl group, a hydroxyalkyl group or an aryl group, R⁶ stands for amonovalent, electron-attractive atom or organic group, and n is aninteger of from 0 to 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The radical-polymerizable monomer (a) used for the photocurablecomposition of the present invention is an ordinaryradical-polymerizable monomer having a carbon-to-carbon unsaturation.More specifically, the monomer (a) includes an unsaturated carboxylicacid monomer, an ester type unsaturated monomer, a nitride typeunsaturated monomer and an aromatic vinyl compound. As the unsaturatedcarboxylic acid monomer, there can be mentioned acrylic acid andmethacrylic acid. As the ester type unsaturated monomer, there can bementioned ordinary (meth)acrylic acid ester type monomers andunsaturated esters of lower aliphatic carboxylic acids such as vinylacetate and allyl acetate. As the nitrile type unsaturated monomer,there can be mentioned acrylonitrile and methacrylonitrile. As thearomatic vinyl compound, there can be mentioned styrene,α-methylstyrene, vinyltoluene and isopropenyltoluene.

Specifically, the (meth)acrylic acid ester type monomer is a(meth)acrylic acid ester type compound formed from acrylic acid ormethacrylic acid and a monohydroxyl or polyhydroxyl compound. Morespecifically, there can be mentioned alkyl (meth)acrylates such asmethyl(meth)acrylate and ethyl(meth)acrylate, and2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, ethyleneglycol di(meth)acrylate, propylene glycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, butyleneglycol di(meth)acrylate, hexylene glycol di(meth)acrylate,2,2-bis[4-(meth)acryloyloxyphenyl]propane,1,3-di(meth)acryloyloxyethoxybenzene,2,2-bis[4-(meth)acryloyloxycyclohexyl]propane,2,2-bis[3-(meth)acryloyloxy-2-hydroxypropoxyphenyl]propane, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate anddipentaerythritol hexa(meth)acrylate.

As another compound belonging to the (meth)acrylic acid ester typemonomer, there can be mentioned an aromatic polycarboxylic acid or itsanhydride having at least one (meth)acryloyloxyl group in the molecule.The (meth)acryloyloxyl group-containing aromatic polycarboxylic acid orits anhydride is a compound having an ester structure formed by reactingat least one hydroxyl group of an alkane polyol or polyoxyalkane polyolhaving at least two hydroxyl groups in the molecule with one carboxylgroup of an aromatic polycarboxylic acid having at least three carboxylgroups in the molecule.

As the alkane polyol having at least two hydroxyl groups in themolecule, which constitutes the (meth)acryloyloxyl group-containingaromatic polycarboxylic acid (a), there can be mentioned ethyleneglycol, 1,2-propylene glycol, 1,3-propylene glycol, butylene glycol,trimethylol propane, glycerol and pentaerythritol. As the polyoxyalkanepolyol having at least two hydroxyl groups in the molecule, there can bementioned diethylene glycol, triethylene glycol, tetraethylene glycol,dipropylene glycol, dibutylene glycol, ditrimethylol propane,diglycerol, triglycerol and dipentaerythritol, and compounds representedby the following formulae: ##STR4##

As the (meth)acrylic acid component constituting the (meth)acryloyloxylgroup-containing aromatic polycarboxylic acid, there can be mentionedacrylic acid and methacrylic acid. An aromatic polycarboxylic acid inwhich at least two carboxyl groups are bonded to adjacent carbon atomson the aromatic nucleus is preferred as the aromatic polycarboxylic acidcomponent having at least three carboxyl groups. More specifically,there can be mentioned hemimellitic acid, trimellitic acid, prehniticacid, mellophanic acid and pyromellitic acid.

As the (meth)acryloyloxyl group-containing aromatic polycarboxylic acidor its anhydride, there can be mentioned4-(meth)acryloyloxymethoxycarbonyl phthalic acid or its anhydride,4-(meth)acryloyloxyethoxycarbonylphthalic acid or its anhydride,4-[2-hydroxy-3-(meth)acryloyloxypropoxycarbonyl]phthalic acid or itsanhydride, 2,3-bis(3,4-dicarboxybenzoyloxy)propyl(meth)acrylate or itsanhydride and 2(3,4-dicarboxy)propane or its anhydride, and compoundsrepresented by the following formulae: ##STR5## wherein R stands for ahydrogen atom or a methyl group, or acid anhydrides of these compounds.Among the above-exemplified compounds,4-(meth)acryloyloxyethoxycarbonylphthalic acid or its anhydride ispreferred, and 4-(meth)acryloyloxyethoxycarbonylphthalic anhydride isespecially preferred.

The foregoing radical-polymerizable monomers may be used singly or inthe form of mixtures of two or more of them. However, when thephotocurable composition of the present invention is used as a dentalresin composition, there is preferably used a monomer mixture comprising(i) an ester monomer of an aliphatic alcohol or aliphatic polyol withmethacrylic acid and (ii) at least one monomer selected from the groupconsisting of an ester of a polyol having a bisphenol skeleton ordihydric phenol skeleton with methacrylic acid and a methacryloxylgroup-containing aromatic polycarboxylic acid or its anhydride. Themonomers (i) and (ii) may be used at a (i)/(ii) weight ratio of from5/95 to 95/5.

The photopolymerization initiator to be incorporated into thephotocurable composition of the present invention consists of anα-ketocarbonyl compound (b) and an amine (c). The α-ketocarbonylcompound includes an α-diketone, an α-ketoaldehyde, an α-ketocarboxylicacid and an α-ketocarboxylic acid ester. More specifically, there can bementioned α-diketones such as diacetyl, 2,3-pentadione, 2,3-hexadione,benzil, 4,4'-dimethoxybenzil, 4,4'-diethoxybenzil, 4,4'-oxybenzil,4,4'-dichlorobenzil, 4-nitrobenzil, α-naphthil, β-naphthil,camphorquinone and 1,2-cyclohexanedione, α-ketoaldehydes such asmethylglyoxal and phenylglyoxal, and pyruvic acid, benzoylformic acid,phenylpyruvic acid, methyl pyruvate, ethyl benzoylformate, methylphenylpyruvate and butyl phenylpyruvate. Among these α-ketocarbonylcompounds, α-diketones are preferably used from the viewpoint of thestability or the like. Among α-diketones, diacetyl, benzil andcamphorquinone are preferred, and camphorquinone is especiallypreferred.

In the composition of the present invention, an amine selected fromspecific amines described below is used as the amine.

As the amine of the first group, there can be mentioned aromaticcompounds represented by the following general formula (1): ##STR6##wherein X stands for >NR², an oxygen atom or a sulfur atom, Y stands fora hydrogen atom, --SR³ or a monovalent, divalent or trivalent metal, thenumber of the residue ##STR7## is 1 or the same as the valency number ofthe metal when Y is a divalent or trivalent metal, R¹ stands for analkyl, aryl or aralkyl group ordinarily having 1 to 20 carbon atoms, ora halogen atom, n is an integer of from 0 to 4, with the proviso thatwhen n is 2 or larger, a plurality of the groups R¹ may be the same ordifferent, R² stands for a hydrogen atom, an alkyl, aryl or aralkylgroup ordinarily having 1 to 20 carbon atoms, and R³ stands for an alkylgroup or an aryl group, or a group represented by the following generalformula (2): ##STR8## wherein X, R¹ and n are as defined above.

As specific examples of R¹ in the above-mentioned aromatic sulfurcompound of the formula (1), there can be mentioned a hydrogen atom,alkyl groups ordinarily having 1 to 6 carbon atoms, such as methyl,ethyl, propyl, butyl, pentyl and hexyl groups, aryl groups ordinarilyhaving 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, cumyl andnaphthyl groups, aralkyl groups ordinarily having 7 to 20 carbon atoms,such as benzyl, phenylethyl, phenylisopropyl, naphthylmethyl andnaphthylethyl groups, and halogen atoms such as fluorine, chlorine,bromine and iodine. As specific examples of R², there can be mentioned ahydrogen atom and alkyl, aryl and aralkyl groups exemplified above asR¹. As specific examples of R³, there can be mentioned alkyl and arylgroups exemplified above as R¹. As specific examples of the grouprepresented by the general formula (2), there can be mentioned abenzimidazole group, a benzoxazole group, a benzothiazole group, amethylbenzimidazole group, a methylbenzoxazole group and amethylbenzothiazole group. As specific examples or Y, there can bementioned a hydrogen atom, metals of the group Ia such as lithium,sodium and potassium, metals of the group Ib such as copper and silver,metals of the group IIa such as magnesium, calcium, strontium andbarium, metals of the group IIb such as zinc, cadmium and mercury,metals of the group III such as alminum, gallium and yttrium, and metalsof the groups VIb, VIIb and VIII such as chromium, molybdenum,manganese, iron, cobalt, nickel, ruthenium, rhodium and palladium.

As specific examples of the aromatic compound (c) represented by thegeneral formula (2), there can be mentioned 2-mercaptobenzimidazole,2-mercaptobenzoxazole, 2-mercaptobenzothiazole,2-mercaptomethylbenzimidazole, 2-mercaptomethylbenzoxazole,2-mercaptomethylbenzothiazole, dibenzooxazyl disulfide, dibenzothiazyldisulfide, 2-(phenylthio)benzothiazole, sodium 2-mercaptobenzimidazole,zinc (II) 2-mercaptobenzimidezole, copper (II) 2-mercaptobenzimidazole,nickel (II) 2-mercaptobenzimidazole, zinc (II) 2-mercaptobenzothiazole,copper (II) 2-mercaptobenzotiazole, zinc (II)2-mercaptomethylbenzimidazole, zinc (II) 2-mercaptomethylbenzothiazole,2-mercaptodimethylbenzimidazole, 2-mercaptodimethylbenzoxazole,2-mercaptodimethylbenzothiazole and 2-mercaptotetramethylbenzothiazole.Among these sulfur compounds, there are preferably used2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole,2-mercaptomethylbenzothiazole, dibenzothiazyl disulfide, zinc (II)2-mercaptobenzimidazole, zinc (II) 2-mercaptobenzothiazole and zinc (II)2-mercaptomethylbenzothiazole, and 2-mercaptobenzothiazole,2-mercaptomethylbenzothiazole, zinc (II) 2-mercaptobenzothiazole andzinc (II) 2-mercaptomethylbenzothiazole.

These amines are prominently characterized in that they contain amercapto group (--S--) in addition to the nitrogen atom contained in the5-membered ring. These amines are advantageous over the known amines inthat the curing speed at low temperatures is high and it provides acured product having no substantial discoloration and a good waterresistance.

Amines of another group used in the photocurable composition of thepresent invention are nucleus-substituted amines represented by thefollowing general formula (3): ##STR9##

In the above general formula (3), R⁴ stands for a hydrogen atom or analkyl group ordinarily having 1 to 6 carbon atoms, such as a methyl,ethyl, propyl, butyl, pentyl or hexyl group. R⁵ stands for a hydrogenatom, an alkyl group having 1 to 6 carbon atoms, such as mentionedabove, a hydroxyalkyl group such as a hydroxymethyl, 2-hydroxyethyl,2-hydroxypropyl, hydroxybutyl, hydroxypentyl or hydroxyhexyl group, oran aryl group such as a phenyl, tolyl, ethylphenyl, propylphenyl,isopropylphenyl, dimethylphenyl, fluorophenyl, chlorophenyl,dichlorophenyl, bromophenyl, methoxyphenyl, ethoxyphenyl,isopropoxyphenyl, dimethoxyphenyl, nitrophenyl or dinitrophenyl group.R⁶ stands for a monovalent, electron-attractive atom or organic group,and it is especially preferred that R⁶ be a group represented by thefollowing general formula (4): ##STR10## wherein R⁷ stands for ahydrogen atom or an alkyl, hydroxyalkyl or aryl group as exemplifiedabove with respect to R⁵, or a hydroxyl group, an alkoxyl groupordinarily having 1 to 6 carbon atoms, such as a methoxyl, ethoxyl,propoxyl or butoxyl group, or an amino group of the formula --NR⁸ R⁹ inwhich R⁸ R⁹ stand for a hydrogen atom or an alkyl group having 1 to 4carbon atoms, such as exemplified above with respect to R⁴.

An aniline derivative substituted by an electron-attractive group,especially a group represented by the general formula (4), is excellentover an analogous aniline derivative free of such a substituent in thecuring speed at room temperature and provides a cured product having nodiscoloration and improved physical properties.

As the above-mentioned substituted aromatic amine, there can bementioned 4-dimethylaminobenzaldehyde, 4-diethylaminobenzaldehyde,4-(methylhexylamino)benzaldehyde, 4-(methylphenylamino)benzaldehyde,4-(β-hydroxyethylmethylamino)benzaldehyde, 4-dimethylaminobenzoic acid,4-diethylaminobenzoic acid, 4-(methylhexylamino)benzoic acid,4-(β-hydroxyethylmethylamino)benzoic acid, methyl4-dimethylaminobenzoate, methyl 4-diethylaminobenzoate, methyl4-dipropylaminobenzoate, methyl 4-(methylhexylamino)benzoate, methyl4-(methylphenylamino)benzoate, propyl4-(β-hydroxyethylmethylamino)benzoate, hexyl 4-dimethylaminobenzoate,phenyl 4-dimethylaminobenzoate, 4-dimethylaminophthalic acid,4-dimethylaminoisophthalic acid and dimethyl4-dimethylaminoisophthalate. Among these substituted aromatic amines,4-dimethylaminobenzaldehyde, 4-dimethylaminobenzoic acid and methyl4-dimethylaminobenzoate are preferred.

As the electron-attractive group other than those represented by thegeneral formula (4), there can be mentioned a cyano group, a nitro groupand a halogen atom in the order of importance. The aromatic amine ofthis type is slightly inferior to an amine having a substituentrepresented by the general formula (4) in the curing speed. However, ananiline derivative nucleus-substituted with a cyano group is superior toan aniline derivative having an alkyl chain substituted with a cyanogroup in the curing speed at normal temperature. As specific examples ofthe aromatic amine of this type, there can be mentionedN,N-dimethyl-o-cyanoaniline, N,N-dimethyl-o-nitroaniline,N,N-dimethyl-o-chloroaniline, N,N-dimethl-o-bromoaniline,N,N-dimethyl-o-iodoaniline, N,N-dimethyl-m-cyanoaniline,N,N-dimethyl-m-nitroaniline, N,N-dimethyl-m-chloroaniline,N,N-dimethyl-m-nitroaniline, N,N-dimethyl-m-chloroaniline,N,N-dimethyl-m-bromoaniline, N,N-dimethyl-p-cyanoaniline,N,N-dimethyl-p-nitroaniline, N,N-dimethyl-p-chloroaniline,N,N-dimethyl-p-bromoaniline, N,N-diethyl-o-cyanoaniline,N,N-diethyl-m-cyanoaniline, N,N-diethyl-p-cyanoaniline,N,N-diethyl-p-chloroaniline, N,N-dipropyl-p-cyanoaniline,N,N-dibutyl-p-cyanoaniline, N,N-methylphenyl-p-cyanoaniline,N,N-β-hydroxyethylmethyl-p-chloroaniline,N,N-dimethyl-2,4-dicyanoaniline, N,N-dimethyl-2,4-dinitroaniline andN,N-dimethyl-2,4-dichloroaniline. Among these substituted aromaticamines, N,N-dimethyl-p-cyanoaniline and N,N-diethyl-p-cyanoaniline arepreferred.

It should be understood that in the composition of the presentinvention, the α-diketone, α-ketoaldehyde, α-ketocarboxylic acid orsubstituted amine may be present in the form bonded to the side chain orterminal of the polymer.

In the photocurable composition of the present invention, theα-ketocarbonyl compound is incorporated in an amount of 0.01 to 15 partsby weight, preferably 0.05 to 10 parts by weight, per 100 parts byweight of the radical-polymerizable monomer and the substituted aromaticamine is incorporated in an mount of 0.01 to 15 parts by weight,preferably 0.05 to 10 parts by weight, per 100 parts by weight of theradical-polymerizable monomer. The molar ratio of the substitutedaromatic amine to the α-ketocarbonyl compound is ordinarily in the rangeof from 0.1 to 10, preferably in the range of from 0.2 to 5.

If necessary, the photocurable composition of the present invention mayfurther comprise other components such as a powdery inorganic filler, anorganic polymer, a tackifier, a photosensitizer, a polymerizationmodifier and a polymerization inhibitor. As the powdery inorganicfiller, there can be mentioned, for example, kaolin, talc, clay, calciumcarbonate, silica, silica-alumina, alumina, titanium oxide, calciumphosphate, glass powder and quartz powder. As the organic polymer, therecan be mentioned a wax, an ethylene-vinyl acetate copolymer polymethylmethacrylate and polymethyl acrylate. These components may beincorporated in optional amounts.

When the photocurable composition of the present invention is irradiatedwith light, polymerization is caused to cure the composition. Both thenatural rays and artificial rays may be used as the light, and rays ofthe ultraviolet and visible regions can be adopted. For production ofartifical rays, there may be used a high pressure mercury lamp, a mediumpressure mercury lamp, a low pressure mercury lamp, a halogen lamp and atungsten lamp. The temperature adopted for the photocuring reaction isordinarily 0° to 80° C., preferably 5° to 50° C., and irradiation isordinarily conducted for 1 second to 5 minutes.

The present invention will now be described in detail with reference tothe following examples that by no means limit the scope of theinvention.

EXAMPLE 1

A mixture comprising 70 g of triethylene glycol dimethacrylate, 25 g of2,2-bis[4-(3-methacryloyloxypropoxy)phenyl]propane, 5 g of4-methacryloyloxyethoxycarbonylphthalic anhydride and 50 g of finelydivided silica (Aerosil R-972 supplied by Nippon Aerosil K.K.) waskneaded at room temperature by two rolls to form a composition. On onesurface of a polypropylene plate having a thickness of 3 mm and acircular through hole having a diameter of 3 mm was placed anotherpolypropylene plate, and 2 g of the above composition, 5 mg ofcamphorquinone and 5 mg of 4-dimethylaminobenzaldehyde were sufficientlymixed by a spatula and the resulting photocurable composition was packedinto the circular hole. Visible rays (having a wavelength of 350 to 700nm) were applied by using a visible ray irradiator (Translux supplied byKulzer Co.) set 1 cm above the photocurable composition. The curing timeand the color tone of the cured product were examined. The curing timewas expressed by the shortest visible ray irradiation time necessary forreducing the penetration (under a load of 1 kg) to zero on the surfaceof the cured product opposite to the visible ray-irradiated surface. Theobtained results are shown in Table 1.

EXAMPLES 2 THROUGH 23 AND COMPARATIVE EXAMPLES 1 THROUGH 5

Photocurable compositions were prepared in the same manner as describedin Example 1 except that compounds shown in Table 1 were used in amountsshown in Table 1 as the α-ketocarbonyl compound and substituted aromaticamine instead of camphorquinone and 4-dimethylaminobenzaldehyde used inExample 1, and the curing times and color tones of these compositionswere examined in the same manner as described in Example 1. The obtainedresults are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________           α-Ketocarbonyl        Curing                                                                             Color Tone                            Example                                                                              Compound                    time of Cured                              No.    (amount, mg)                                                                             Amine (amount, mg)                                                                             (seconds)                                                                          Product                               __________________________________________________________________________       1   camphorquinone (5)                                                                       4-dimethylaminobenz-                                                                           25   colorless                                               aldehyde (5)                                                   2   camphorquinone (5)                                                                       4-dimethylaminobenzene                                                                         30   "                                                       acid                                                           3   camphorquinone (5)                                                                       methyl 4-dimethylamino-                                                                        20   "                                                       benzoate (5)                                                .[.4   benzil (5) methyl 4-dimethylamino-                                                                        35    ".].                                                   benzoate (5)                                                4.[.5.].                                                                             diacetyl (5)                                                                             methyl 4-dimethylamino-                                                                        25   "                                                       benzoate (5)                                                5.[.6.].                                                                             camphorquinone (5)                                                                       4-dimethylaminobenz-                                                                           20   "                                                       aldehyde (10)                                               6.[.7.].                                                                             camphorquinone (20)                                                                      methyl 4-dimethylamino-                                                                        15   "                                                       benzoate (10)                                               7.[.8.].                                                                             camphorquinone (5)                                                                       2-mercaptobenzimidazole (5)                                                                    15   "                                     8.[.9.].                                                                             camphorquinone (5)                                                                       2-mercaptobenzothiazole (5)                                                                    30   "                                     9.[.10.].                                                                            camphorquinone (5)                                                                       2-mercaptobenzoxazole (5)                                                                      35   "                                     .[.11.].10                                                                           camphorquinone (5)                                                                       2-mercaptomethylbenzothiazole (5)                                                              30   "                                     11.[.12.].                                                                           camphorquinone (5)                                                                       zinc (II) 2-mercaptomethyl-                                                                    30   "                                                       benzothiazole (5)                                           12.[.13.].                                                                           camphorquinone (5)                                                                       zinc (II) 2-mercaptomethyl-                                                                    35   "                                                       benzooxazole (5)                                            .[.14  benzil (5) 2-mercaptobenzothiazole (5)                                                                    35    ".].                                 13.[.15.].                                                                           diacetyl (5)                                                                             2-mercaptobenzothiazole (5)                                                                    35   "                                     .[.16.].14                                                                           camphorquinone (10)                                                                      2-mercaptobenzothiazole (10)                                                                   25   "                                     15.[.17.].                                                                           camphorquinone (20)                                                                      2-mercaptobenzothiazole (10)                                                                   20   "                                     .[.18.].16                                                                           camphorquinone (5)                                                                       N,N-dimethyl-p-cyanoaniline (5)                                                                30   "                                     .[.19.].17                                                                           camphorquinone (5)                                                                       N,N-diethyl-p-cyanoaniline (5)                                                                 30   "                                     .[.20  benzil (5) N,N-dimethyl-p-cyanoaniline (5)                                                                35    ".].                                 18.[.21.].                                                                           diacetyl (10)                                                                            N,N-dimethyl-p-cyanoaniline (10)                                                               35   "                                     19.[.22.].                                                                           camphorquinone (20)                                                                      N,N-dimethyl-p-cyanoaniline (15)                                                               25   "                                      20.[.23.].                                                                          camphorquinone (20)                                                                      N,N-dimethyl-p-cyanoaniline (20)                                                               20   "                                     Comparative                                                                          camphorquinone (5)                                                                       tri-n-hexylamine (5)                                                                           >180 "                                     Example 1                                                                     Comparative                                                                          camphorquinone (5)                                                                       N,N-dimethylaniline (5)                                                                        40   yellow                                Example 2                                                                     Comparative                                                                          camphorquinone (5)                                                                       N-methyl-N-2-cyanoethylaniline                                                                 40   "                                     Example 3         (5)                                                         Comparative                                                                          camphorquinone (5)                                                                       N-methyl-N-2-chloroethyl-                                                                      45   light                                 Example 4         aniline (5)           yellow                                Comparative                                                                          camphorquinone (5)                                                                       N-methyl-N-2-cyanoethyl-p-                                                                     45   light                                 Example 5         nitroaniline (5)      yellow                                __________________________________________________________________________

EXAMPLE .[.24.]. .Iadd.21 .Iaddend.

A photocurable liner was prepared by adding 30 mg of camphorquinone and30 mg of methyl 4-dimethylaminobenzoate to 3 g of a primer compositioncomprising 93 parts by weight of methyl methacrylate. 5 parts by weightof 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane and 2parts byweight of 4-methacryloyloxyethoxycarbonylphthalic anhydride. Ahole having a diameter of 3 mm and a depth of 2 mm was formed in abovine anterior tooth lip and etching was carried out for 45 secondswith a 65% aqueous solution of phosphoric acid, followed by waterwashing and drying. The above-mentioned liner was thinly coated on thecircular hole of the bovine tooth. Than a photocurable compositionformed by sufficiently mixing by a spatula 7 g of triethylene glycoldimethacrylate, 2.5 g of2,2-bis[4-(3-methacryloyloxy-2hydroxypropoxy)phenyl]propane, 5 g offinely divided silica (Aerosil R-972 supplied by Nippon Aerosil K.K.),40 mg of camphorquinone and 40 mg of methyl 4-dimethylaminobenzoate wasfilled in the liner-treated circular hole of the bovine tooth, andvisible rays were applied for 2 minutes to cure the photocurablecomposition.

The sample was immersed in water overnight, and in order to examine thefilled state, the sample was immersed in cold water at 4° C. and warmwater at 60° C. alternately at intervals of 1 minute 60 times as a wholefor a total immersion time of 2 hours. Then, removal of the filledsubstance by a pincette was tried, but it was impossible to remove thefilled substance from the dentine.

COMPARATIVE EXAMPLE 6

A photocurable liner and a photocurable composition were prepared in thesame manner as in Example 24 except that4-methacryloyloxyethoxycarbonylphthalic anhydride was not incorporatedin the photocurable liner and 40 mg of N,N-dimethylaniline was used forthe photocurable composition instead of 40 mg of methyl4-dimethylaminobenzoate, and the filling operation was carried out on abovine tooth in the same manner as described in Example 24. In the samemanner as described in Example 24, the sample was immersed in water andsubjected to the heat cycle test. When removal of the filled substanceby a pincette was tried, the filled substance was easily peeled from thedentine.

EXAMPLE .[.25.]. .Iadd.22 .Iaddend.

A photocurable liner was prepared in the same manner as described inExample 24 except that 2-mercaptobenzothiazole was used instead ofmethyl 4-dimethylaminobenzoate, and a circular hole of a bovine toothwas treated with this liner in the same manner as described in Example24. A photocurable composition formed by sufficiently mixing by aspatula 5 g of triethylene glycol dimethacrylate, 5 g of2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane. 10 g offinely divided silica (Aerosil RM-50 supplied by Nippon Aerosil K.K.),40 mg of camphorquinone and 40 mg of 2-mercaptobenzothiazole was filledin the liner-treated circular hole of the bovine tooth, and irradiationwith visible rays was conducted for 30 seconds to cure the photocurablecomposition.

The sample was immersed in water overnight, and in order to examine thefilled state, the sample was immersed in cold water at 4° C. and warmwater at 60° C. alternately at intervals of 1 minute 60 times as a wholefor a total immersion time of 2 hours. When removal of the filledsubstance by a pincette was tried, the filled substance was not peeledfrom the dentine.

EXAMPLE .[.26.]. .Iadd.23 .Iaddend.

The experiment was carried out in the same manner as described inExample 25 except that N,N-dimethyl-p-cyanoaniline was used instead of2-mercaptobenzothiazole. Results similar to those obtained in Example 25were obtained.

EXAMPLE .[.27.]. .Iadd.24 .Iaddend.

A bovine tooth hole was treated with the same liner as used in Example24, and a photocurable composition formed by sufficiently mixing by aspatula 5 g of triethylene glycol, 5 g of1,3-dimethacryloyloxyethoxybenzene, 10 g of finely divided silica(Aerosil RM50 supplied by Nippon Aerosil K.K.), 30 mg of camphorquinoneand 30 mg of methyl 4-dimethylaminobenzoate was filled in theliner-treated tooth hole. Irradiation with visible rays was conductedfor 30 seconds to cure the photocurable composition. The immersion testwas carried out in the same manner as described in Example 24. Resultssimilar to those obtained in Example 24 were obtained.

EXAMPLE .[.28.]. .Iadd.25 .Iaddend.

The enamel of the lip surface of a bovine anterior tooth wassufficiently polished with emery paper No. 6/0 to smooth the surface.The tooth was etched for 45 seconds with a 65% aqueous solution ofphosphoric acid, followed by sufficient washing with water. The etchedsurface was dried by air and a cellophane tape (about 13 mm×about 13 mm)having a circular hole having a diameter of 5.4 mm was applied to theetched surface. The same photocurable liner as described in Example 24was finely coated in the circular hole, and after standing at roomtemperature for 2 minutes, irradiation with visible rays was conductedfor 2 minutes. Two compositions were prepared by sufficiently kneading1% by weight of benzoyl peroxide or 0.6% by weight ofdimethyl-p-toluidine into a kneaded composition comprising 50 parts byweight of triethylene glycol dimethacrylate, 25 parts by weightneopentyl glycol dimethacrylate, 25 parts by weight of2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane and 20parts by weight of finely divided silica. Equal amounts of the twocompositions containing benzoyl peroxide and dimethyl-p-toluidine,respectively, were mixed and kneaded sufficiently with each other. Byusing the so-prepared adhesive composition, an acrylic resin rod havinga diameter of 5 mm was butt-bonded to the linear-treated enamel surfaceof the bovine tooth. The bonded structure was allowed to stand stillovernight. The bonded sample was immersed in cold water at 4 ° C. andwarm water at 60° C. alternately at intervals of 1 minute 60 times as awhole for a total immersion time of 2 hours. Then, the sample wasallowed to stand in air maintained at 23° C. for 10 minutes, and thebonding forth between the bovine tooth and the acrylic resin rod wasmeasured at 23° C. at a pulling speed of 2 mm/min. It was found that thebonding force was 131 Kg/cm².

The bonding test was carried out in the same manner as described aboveby using the photocurable liners used in Examples 25 and 26, and it wasfound that the bonding forces were 120 Kg/cm² and 121 Kg/cm²,respectively.

COMPARATIVE EXAMPLE 7

A bonded test piece was prepared in the same manner as described inExample 28 except that a curable liner formed by adding 30 mg ofcamphorquinone and 30 mg of dimethylaniline to 3 g of a compositioncomprising 95 parts by weight of methyl methacrylate and 5 parts byweight of 2,2-bis[4-methacryloyloxy-2-hydroxypropoxy)phenyl]propane wasused instead of the photocurable liner used in Example 28, and thebonding force between the bovine tooth and the acrylic resin rod wasmeasured in the same manner as described in Example 28. It was foundthat the bonding force was 32 Kg/cm².

We claim: .[.1. A photocurable composition comprising (a) aradical-polymerizable monomer, (b) an α-ketocarbonyl compound and (c) anamine, wherein the amine (c) is at least one member selected from thegroup consisting of compounds represented by the following generalformula: ##STR11## wherein X stands for >NR², an oxygen atom or a sulfuratom, Y stands for a hydrogen atom, --SR³ or a monovalent, divalent ortnvalent metal, R¹ stands for an alkyl group, an aryl group, an aralkylgroup or a halogen atom, n is an integer of from 0 to 4 with the provisothat when n is 2 or larger, a plurality of groups R¹ may be the same ordifferent, R² stands for a hydrogen atom, an alkyl group, an aryl groupor an aralkyl group, and R³ stands for an alkyl group or an aryl group,or a group represented by the following general formula: ##STR12##wherein X, R¹ and n are as defined above, and substituted aminesrepresented by the following general formula: ##STR13## wherein R⁴stands for a hydrogen atom or an alkyl group, R⁵ stands for a hydrogenatom, an alkyl group, a hydroxyalkyl group of an aryl group, R⁶ standsfor a monovalent, electron-attractive atom or organic group, and n is aninteger of from 0 to 4..]. .[.2. A composition as set forth in claim 1,wherein the amine (c) is 2-mercaptobenzothiazole,2-mercaptomethylbenzothiazole, zinc (II) 2-mercaptobenzothiazole or zinc(II) 2-mercaptomethylbenzothiazole..]. .[.3. A composition as set forthin claim 1, wherein the amine (C) is a substituted aromatic aminerepresented by the following general formula: ##STR14## wherein R⁴stands for a hydrogen atom or an alkyl group, R⁵ stands for a hydrogenatom, an alkyl group,, a hydroxyalkyl group or an aryl group, R⁷ standsfor a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxyl group,a hydroxyalkyl group, an aryl group or a group --NR⁸ R⁹ in which R⁸ andR⁹ stand for a hydrogen atom or an alkyl group, and n is an integer offrom 0 to 4..]. .[.4. A composition as set forth in claim 3, wherein thesubstituted aromatic amine is 4-dimethylaminobenzaldehyde,4-dimethylaminobenzoic acid or methyl 4-dimethylaminobenzoate..]. .[.5.A composition as set forth in claim 1, wherein the amine (c) is asubstituted aromatic amine in which R⁶ is a cyano group..]. .[.6. Acomposition as set forth in claim 5, wherein the substituted aromaticamine is N,N-dimethyl-p-cyanoaniline or N,N-diethyl-p-cyanoaniline..]..[.7. A composition as set forth in claim 1, wherein theradical-polymerizable monomer is a monomer having at least one acryloylor methacryloyl group..]. .[.8. A composition as set forth in claim 1,wherein the radical-polymerizable monomer is a combination of (i) anester monomer of an aliphatic alcohol or aliphatic polyol withmethacrylic acid and (ii) at least one monomer selected from the groupconsisting of an ester monomer of a polyol having a bisphenol skeletonor dihydric phenol skeleton with methacrylic acid and a methacryloyloxylgroup-containing aromatic polycarboxylic acid or its anhydride..]. .[.9.A composition as set forth in claim 8, wherein the monomers (i) and (ii)are present at a (i)/(ii) weight ratio of from 5/95 to 95/5..]. .[.10. Acomposition as set forth in claim 1, wherein the α-ketocarbonyl compound(b) is an α-diketone..]. .[.11. A composition as set forth in claim 1,wherein the α-ketocarbonyl compound (b) is benzil or camphorquinone..]..[.12. A composition as set forth in claim 1, wherein the α-ketocarbonylcompound (b) is present in an amount of 0.01 to 15 parts by weight per100 parts by weight of the radical-polymerizable monomer (a) and theamine (c) is present in an amount of 0.01 to 15 parts by weight per 100parts by weight of the radical-polymerizable monomer (a)..]. .[.13. Adental treatment material comprising a composition as set forth in claim1..]. .Iadd.14. A visible ray curable composition for dental treatmentcomprising:(a) a radical-polymerizable monomer, (b) an α-ketocarbonylcompound which is camphorquinone or diacetyl and (c) an aminerepresented by the formula ##STR15## wherein R⁴ and R⁵ represent ethyl,propyl, butyl, pentyl or hexyl, R⁷ represents hydroxy or alkoxy having 1to 6 carbon atoms, (a), (b) and (c) forming a visible ray curable dentalcomposition. .Iaddend. .Iadd.15. The composition as set forth in claim14, wherein radical-polymerizable monomer is a monomer having at leastone acryloyl or methacryloyl qroup. .Iaddend. .Iadd.16. The compositionas set forth in claim 14, wherein the radical-polymerizable monomer is acombination of (i) an ester monomer of an aliphatic alcohol or aliphaticpolyol with methacrylic acid and (ii) at least one monomer selected fromthe group consisting of an ester monomer of a polyol having a bisphenolskeleton or dihydric phenol skeleton with methacrylic acid and amethacryloyloxyl group-containing aromatic polycarboxylic acid or itsanhydride. .Iaddend. .Iadd.17. The composition as set forth in claim 16,wherein the monomers (i) and (ii) are present at a (i)/(ii) weight ratioof from 5/95 to 95/5. .Iaddend. .Iadd.18. The composition of claim 14,wherein the α-ketocarbonyl compound (b) is camphorquinone. .Iaddend..Iadd.19. The composition of claim 14, wherein the α-ketocarbonylcompound (b) is diacetyl. .Iaddend. .Iadd.20. The composition as setforth in claim 14, wherein the α-ketocarbonyl compound (b) is present inan amount of 0.01 to 15 parts by weight per 100 parts by weight of theradical-polymerizable monomer (a) and the amine (c) is present in anamount of 0.01 to 15 parts by weight per 100 parts by weight of theradical-polymerizable monomer (a). .Iaddend. .Iadd.21. The compositionof claim 14, which is diethylaminobenzoic acid or alkyl ester thereof..Iaddend. .Iadd.22. The composition of claim 14, which isdipropylaminobenzoic acid or alkyl ester thereof. .Iaddend. .Iadd.23. Adental material comprising a composition as set forth in claim 14..Iaddend.